1. Field of the Invention
The present invention relates to an imaging apparatus and a control method therefor. More specifically, the present invention relates to an imaging apparatus configured to record image data captured with an imaging unit on a recording medium and a control method therefor.
2. Description of the Related Art
A conventional digital camera converts an image signal of an image captured with an image sensor, such as a charge-coupled device (CCD), into a digital signal, processes the digital signal into a digital video signal including a luminance signal and color-difference signals, then compresses the digital video signal into Joint Photographic Experts Group (JPEG)-coded image data, and records the compressed image data on a recording medium. In recent years, a conventional image sensor in a digital camera has a high resolution of 10,000,000 pixels or more.
Meanwhile, a conventional digital camera, in reading an image signal, can skip reading some of horizontal lines and vertical lines of its image sensor to read image signals and record the read image signals as a moving image at a high speed. Furthermore, in recent years, a conventional digital camera has two image capturing modes, namely, a still image capturing mode and a moving image capturing mode. A user can switch between the two image capturing modes.
In recent years, as discussed in Japanese Patent Application Laid-Open No. 2004-201282, a still image can be captured while a moving image is being recorded. The method discussed in Japanese Patent Application Laid-Open No. 2004-201282 reduces an occurrence of a phenomenon such that in the case of capturing a still image while recording a moving image, a compressed moving image data file generated based on image data captured in a moving image capturing mode, which has been interrupted to start capturing a still image, may be divided into two files across a still image file. More specifically, the method discussed in Japanese Patent Application Laid-Open No. 2004-201282 reduces a phenomenon of divided moving image data files by using one frame of the moving image data located immediately before a still image capturing time period as a substitute frame and consecutively storing the same substitute frame in the moving image data file for a period as long as the time period in which a still image is captured.
Furthermore, Japanese Patent Application Laid-Open No. 2004-201282 discusses a method for synchronizing a timing of resuming moving image capturing processing by an imaging unit once interrupted to start capturing a still image with a period of capturing a moving image frame in the moving image capturing processing performed before being interrupted. Additionally, Japanese Patent Application Laid-Open No. 2003-8948 discusses a method of using special image data or a solid image as a substitute frame to be substituted for a missing moving image frame.
However, in the above-described conventional methods, the file size of a moving image data file may become large because the methods make a copy of a black image (blackout image) or a substitute frame (stop motion image) and insert the black image or the substitute frame into a moving image data file.
Furthermore, in the above-described conventional methods, when the same stop motion image is input in an image codec, the quality of a reference image may become lower than an input image. Thus, a compression ratio may not be as high as expected.